What HMRC says
For system errors that do not begin with "ASM", HMRC's guidance says to check that you have not typed any blank spaces into the spreadsheet before or after donor information.
Where the spaces hide
- At the end of a surname or house number, often from copying out of an email or web page.
- Non-breaking spaces, which look normal but are a different character. These often come from web forms and PDFs.
- Line breaks inside a cell, usually from multi-line address fields in an export.
- Cells that look empty but contain a single space. HMRC says to leave fields that do not apply completely blank.
- Amounts with a £ sign or a comma. HMRC asks for plain numbers to two decimal places, such as 200.00, not £200.
How to find them
- Use Find and Replace to search for two spaces and replace with one, then search for a space at the start or end of cells. In LibreOffice, tick "Regular expressions" and search for
^\s+|\s+$, replacing with nothing. - Click into a cell that should be empty and press Delete, rather than typing a space.
- For amounts, remove £ signs and set the cells to a number format with two decimal places.
Donor Schedule trims spaces, removes line breaks and non-breaking spaces, and writes amounts as plain numbers, so these do not reach the file.
Source: HMRC schedule spreadsheet guidance, "Error messages".
This page is general guidance based on HMRC's published schedule spreadsheet guidance and template, checked on 20 October 2026. It is not tax advice, and HMRC's own pages take priority if they change. Donor Schedule is not affiliated with HMRC.
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